Very spot-on description of the mania-to-blah mindset that does in 95% of blogs. I'd also add to the mix:
1) Unrealistic Expectations. Most people have no idea what "success" really looks like for a blog. They assume that, if six months have gone by and they're not getting 100,000+ followers, they've failed. Another unrealistic expectation is what I'd call an overly generous self-assessment: the blogger in question overestimates how much gas he has in the tank on a particular topic. He may get a few great ideas in his head one day, then build a blog around them, then find himself struggling for material on the third day.
2) Lack of Patience. Building a successful following is rarely an overnight journey. Some blogs take years to find their footing, and years more to find their audiences.
3) Insufficient or Non-Strategic Marketing. As folks in the startup world are well aware, you really need to think outside the box -- and occasionally go totally wild -- to get attention in today's crowded marketplace of ideas. You've also got to be clever about building credibility, connections to the right influencers, and paths outward from those influencers to broader audiences. By contrast, most hobby-bloggers take a "write it and they will come" approach -- hoping naively that people will flock to their blogs as if called to them by magic. Or they'll blast notices out to all their friends and family, rather than taking a careful inventory of who might actually be interested, who might be very interested, and who might be so interested that she'll tell her friends (or, conversely, who might not give a flying you-know-what). It's counterintuitive to think that starting out by telling fewer people is preferable to shotgunning everyone you know. But the shotgun approach seldom works. Start surgically.
As it turns out, probably 90% of the work of building a successful blog takes place outside of the blog. Writing great content is the easy part (and it's not easy!); getting folks to notice is the hard part.